Collocated radio-frequency (RF) technologies may suffer from interference to each other that can cause service interruption or degradation of link or packet-level performance. Such interferences can be due to a number of factors, for example, physical proximity, spectral adjacency, imperfection of RF filtering that drifts with temperature, and RF harmonics or intermediate modulations with transmissions associated with multiple radio technologies. Even simultaneous transmission (Tx) and receiving (Rx) of the same RF technology over the same or different carriers, such as long-term evolution (LTE) carrier aggregation and LTE/3G data-plus-2G voice, may encounter the interference problem. For instance, wireless local-area network (WLAN) and Bluetooth (BT) can both operate at 2.4 GHz industrial, scientific, and medical (ISM) band, and cannot be resolved by purely radio-frequency (RF)-level filtering for a single-die WLAN-BT combo chip.
In LTE, time-division duplexing (TDD) transmission and reception are done based on time division such that a ten milli-second (ms) frame is split into one-ms uplink (UL) transmission occasions and one-ms Downlink (DL) transmission occasions. To achieve time division coexistence between LTE and WLAN, BT-special-interest group (SIG) has specified a wireless-coexistence interface-2 (WCI-2) protocol that allows LTE to provide WLAN with LTE UL occasion and LTE DL occasion signals, so that LTE and WLAN transceivers can synchronize their UL/DL transmissions. A WLAN transmitter can perform its WLAN UL transmissions or DL activities when it receives an LTE uplink transmission occasion signal (e.g., a WCI-2 Type 0 message).